1. Technical Field
The disclosure generally relates to a personal listening device having self-adjusting of the sound volume thereof.
2. Description of Related Art
Headphones and earphones are commonly used as personal listening devices. A typical headphone or earphone has a small-sized built-in speaker, and thus has a size and a shape suitable for attachment to a human ear. These personal listening devices directly output sound received from a sound playing device, such as an MP3 (Moving Picture Experts Group, audio layer 3) player. The personal listening device is worn close to the eardrum, and the sound vibration experienced by the eardrum may be great. Therefore, when a user wears the personal listening device for a long time or uses it at high volume, the eardrum may endure strong vibrations. The user may feel uncomfortable to the point of fatigue, and may even experience illness. Although users may adjust the sound volume by operating a volume control switch, many users still fail to regulate the volume when they are not paying full attention to the sound.